Printing methods and apparatus



May 21, 1957 c. w. JACOB PRINTING METHODS AND APPARATUS 3 Sheets-Sheet 1 Filed Oct. 3, 1952 INVENTOR. CARLYLE If JACOB u anllill l ATTORNEY May 21, 1957 c. w. JACOB 2,792,780

PRINTING METHODS AND APPARATUS Filed 001;. 3, 1952 3 Sheets-Sheet 2 IIIIIIIIIIIIIIIIIII INVENTOR- GARLYLE Ii JACOB H64. @Qaak ATTORNEY May 21, 1957 c. w. JACOB 2,792,780

PRINTING METHODS AND APPARATUS Filed Oct. 3, 1952 3 Sheets-Sheet 3 INVENTOR. CARLYLE n! JACOB ATTORNEY United States Patent 1 2,792,780 PRINTING METHODS AND APPARATUS Carlyle W. Jacob, Rochester, N. Y. Application October 3, 1952, Serial No. 313,019 9 Claims. (Cl. 161-419) This invention relates to a method and apparatus for printing, and more particularly to a method and apparatus, wherein the printing operation is accomplished with out the printing plate contacting the print receiving medium.

Heretofore, material has been printed generally by such conventional methods as letterpress, lithography, or gravure. In each of these methods a plate, or an equivalent element containing a symbol to be printed, comes into physical contact, with the material to be printed. As a result of this direct contact, it has been found necessary to carefully select only papers having the required fiber strength, porosity, and degree of smoothness. Such papers are frequently expensive and not easily procureable. Further, the speed of such printing operations is limited by the time required for the inks to dry. This is especially the case in multi-color operations. Also, where half-tone dot structures are employed, it has not been uncommon to experience the undesirable irregular spreading out of the half-tone dots. This problem has been alleviated to some extent only, by the use of expensive inks and papers.

It is the primary object of this invention to provide a method and an apparatus for printing, wherein the printing plate does not come into direct physical contact with the material to be printed.

Another object of this invention is to provide a method and an apparatus wherein material may be printed by means of passing a stream of marking particles through a printing plate which is located adjacent but spaced from the material.

Another object of this invention is to provide a meth- 0d and an apparatus for priting wherein a flow of ink particles is given a high velocity and collimated and then passed through a printing plate into contact with a print receiving medium.

A still further object of this invention is to provide an apparatus, of the character described, wherein the pattern to be printed is located on a rotatable hollow cylinder which is disposed adjacent to, but spaced from, a cylindrical drum rotating synchronously therewith and hav ing mounted thereon the material to be printed.

A still further object of this invention is to provide a method and apparatus, of the character described, wherein a flow of gas containing therein a suspension of ink particles is produced, and wherein the gas is removed from the flow to leave a collimated beam of ink particles to be passed through a printing plate into contact with a print receiving medium.

Another object of this invention is to provide a method and an apparatus for printing wherein relatively cheap and porous papers may be employed as print receiving mediurns.

Still another object of this invention is the provision of a method and an apparatus for printing wherein heavy in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed can be made within the scope of what is claimed without departing from the spirit of the invention.

The invention is illustrated in the accompanying drawing, wherein:

Figure l is a side elevational view partly in section and showing somewhat diagrammatically one form of the apparatus constituting this invention.

Figure 2 is a front elevational view of the device of Figure l and shown partly in section to thereby expose a part of the interior structure, hereinafter referred to as the collimating section and the droplet chamber.

Figure 3 is a vertical section of a portion of a preferred embodiment of the collimating structure constituting part of the invention herein and taken along lines 3--3 of Figure 4.

Figure 4 is a horizontal section taken along the lines 4--4 of Figure 3.

Figure 5 is a vertical section of a portion of a modified form of collimating structure forming a part of this invention.

Figure 6 is a vertical section of a portion of another form of a collimating structure forming a part of this invention.

Figure 7 is a vertical section of a portion of another form of collimating structure forming a part of this invention.

Figure 8 is a vertical section of a modified form of an ink supplying means and collimating structure forming a part of this invention, shown disposed adjacent to a fragment of a printing plate.

Referring in particular to Figures 1 and 2 of the drawing, a frame 20 is provided having a base portion 21 which is secured to a supporting surface by means of bolts 22. A pair of parallel upright portions 23 and Marc carried by the base portion 21. The upper end 25 of the upright 23 is provided with an opening 26 through which extends a hollow shaft 27. The hollow shaft 27 supports at its end a substantially U-shaped duct 28. The upper end 25 of the upright 23 is provided with a hearing surface 29, which in turn supports a rotatable wheel 30 having a hub portion 31 and a peripheral flange portion 32.

The upright 24 has an upper end 33 which is provided with an opening 34 in which is suitably supported a rotatable shaft 35. The rotatable shaft 35 has secured to its inner end a wheel 36 having a peripheral flange portion 37. Transverse, substantially V-notched bars 38, 38' are suitably connected to the peripheral flange portions 32 and 37 of the wheels 30 and 36 respectively, so that the latter rotate in synchronism.

A thin printing plate is mounted around the peripheral flange portions 32 and 37 to thereby define a hollow printing cylinder 39. The printing cylinder 39 is held in position thereon by means of clamping rings 40, 40' and transverse triangular bars 41, 41' secured to bars 38, 38' by screws 19.

The outer end of the shaft 35 is suitably connected to a drive mechanism through a system of gears 43. A cover 42 is provided to cover the printing plate 39 to thereby minimize the deposits thereon of lint, dirt, or other foreign particles.

A drum 44 rotated about a shaft 45 and having paper 46, to be printed and mounted thereon, is positioned adjacent the printing plate 39. The drum 44 is preferably spaced about 1 of an inch from'the printing cylinder 39.

The shafts 45 and 35 are preferably rotated by means of a common power source, so that one is rotated in a clockwise direction and the other in counterclockwise direction. The circumferential velocity of the printing plate 39 is equivalent to that of the drum 44.

The U-shaped duct 28 has mounted on one leg thereof an ink injector system 50 similar to the system shown in my Patent No. 2,577,894 issued on December ll, .1951. The ink injector 51} produces. a fine mist of atomized particles of ink which are transported in suspension in a flow of a suitable gas such as air. The inkinjector 50 discharges a mixture of atomized inkparticles and air at high velocity into a droplet chamber section 51 which has a relatively large area, so that the ink particles lose some of their high blast momentum. Theink droplets are carried along smoothly by their air vehicle from the droplet chamber 51 to the guiding vanes 52. The vanes 52 also function inthe capacity ofaparticle size. selector, in that-excessivelylarge droplets are caught on the walls of the vanes due to thehigh inertia of such droplets. Although vanes of the type-in Figure l are shown, it is obvious that other types of particle selectors could be expediently utilized, such as electronic selectors. The vanes 52 couldin fact be eliminated, and yeta substantial amount of particle selection would result, in that the excessively large particles would, due to their relatively high inertia be caught against the inside wall of the bight portion of the U-shaped duct 28. It should also be mentioned, that although the droplet chamber 51 is illustrated inside the printing cylinder 39, it could just as well be outside in which instance suitable ducts would transport the atomized inkparticles to the inside of the printing cylinder 39.

As particularly shown in Figures 3 and -4, thefU- shaped duct 28 is provided with a collimating section .53 in which is located a plurality of vertical vanes 54. The collimating section 53 converges so as to producea narrow passageway 55. The interior wall 59 .of.the collimating section 53, defining the narrow passageway 55, is provided with a plurality of apertures SS-suitably spaced which communicate with suction chambers 57, 57.

The mixture of air-and atomized ink particles having traveled through the vanes 52, passesinto the collimating section 53. The vertical vanes aid in producing a vertical collimation of the flow. The. flow continues, and the ink particle paths are caused to speedup and to converge due to the converging configuration of the collimating section 53. When the fiowreaches the narrow passageway 55, the air vehicle is substantially removed due to the action of the suction chambers 57 and 57', the'latter being connected to a suitable suctionproducing source. The air vehicle is removed not only through the aperturesSS, .but also through the interior wall59, which is constructed of a porous material. 'The remaining flow, which consists almost exclusivelyaof inkparticles traveling at high speeds in relatively still air, is discharged from the narrow passageway 55 towardthe printing cylinder 39. Where holes69 are. present the ink particles pass ina collimated beam through into contact with the paper 46 to be printed.

It. should be mentioned that the vertical vanes'54 should preferably be located some distance from the discharge end of the narrow passageway 55, so as to eliminate .the possibility of there being a shadow cast on the printing plate '39. The ink particles suspended .in the air stream travel in paths which converge'toward the center of the narrow passageway 55. The lateral flow of air through the porous wall 59 and through the apertures 58, imparts a force on the ink particles which tend tovcause. their fiow'paths to diverge. The tendency of the ink particle paths to diverge in the narrow passageway 55is substantially equal to their tendency to converge in this area. Therefore, the converging and diverging forces acting on the ink particles counterbalanceeach other-with. the result that a substantially parallel or collimated .beam ,of ink particles is produced. The deviation of the beam from parallelism should preferably be. less than one'part ,inten to twenty-five.

The interior wall 59 of the collimating section 53, due to its porous surface, has the characteristic of soaking up the ink particles that come in contact with it. The soaked up ink travels through the wall 59 into the suction chambers 57 and 57'. The absorbent action of the wall 59 tends to prevent large accumulations or large droplets of ink particles on the wall 59, which might be blown off into contact with the printing plate, thereby tending to plug the openings 60 in the latter. The action of the suction chambers 57 and 57 not only cause the removal of the air vehicle from the flow, but also tends to remove excessively'small droplets from the flow. Just as excessive large droplets tend to plug the openings or the half-tones holes 64), excessively small particlesare undesirable in that they do not possess 'sufiicient momenturn to move in relatively straightlines toward the printing cylinder 39 and the paper 46. Thus, excessively large particles and excessively small particles, together with the air vehicle are removed by the time the fiow is discharged from the narrow passageway 55, leaving a collimated beam of relatively small atomized .particles ofink traveling in a relatively still medium of air.

It should be mentioned that it is undesirable that the beam 'of'ink droplets striking the printing cylinder 39 be encumbered by an air flow, due to the fact that such air flow would tend to distortthe straight line motion of the ink droplets. Also, if there is excessive airflow in the vicinity of the portion of the printing plate 3? adjacent the exit of the passageway 55, some of this air flow is apt to pass through some of the openings or halftone holes 60, thereby causing an undesirable deflection of the flow of ink droplets before the latter strikes the paper 46.

It should be mentioned that absolutely perfect collimation of the ink particle paths is not generally desired, due to the fact thata slight divergence of the beam is necessaryin order to cause one half-tone dot to spread toward the adjacent halftone dot to thereby produce acontinuous tone. Normally it is desirable that each half-tone dot be enlarged sulliciently to meet its:neighboring or adjacent dots so as to produce a-continuous tonal effect.

The spreading of the half-tone dots is controlled by several factors, such as spacing of the printing cylinder 39 from the paper 46, the degree of particle size selection, and the extent of the collimation. It is preferable that the .collimating section 53 be directed at a downward angle with respect .to ahorizontaldiametrical axis of the printing cylinder 39.

This angle should be .such that .the downward vertical component of velocityo'f the ink particles is approximately equal to the circumferential velocity of the drum 44. Therefore, the ink particles willtravelthrough the openings 60 .in, a manner .so that they will strike the paper 46 at a pointdirectly across from the particular opening 60 from which theywere discharged. Thus, excessively fine registration is'made possible.

Referring now in particular toFigure l,.a suitable number of fluid jets 63 eject a cleaning fluid 64 onto the printing-cylinder 39. An agitator 65-is located beneath the U-shaped duct 28and produces an agitating action in the cleaning. fluid 64, thereby tending to cleanse the printing cylinder 39, washing the remaining ink from the .same. .An exhaust tube 66 is located adjacent the bottom .of the cover 42 to'thereby control thelevel of the 'cleaning'fluid 64 inside the bottom of the cover or the-enclosure 42. Suitable air jets'67 impart streams of high velocity air against-the printing cylinder 39 to thereby remove the cleaning fluid and any remaining foreign particles from the latter. Suction'linesbS are provided to remove the air from within the enclosure .2, as well1as,:fromlinside. the cylindrical printing cylinder -39. ..;By n:leans .of the suction line "68 located inside' the cylinder 39, the pressure inside the latter can .be con- :veniently: maintained. slightly positive to thereby prevent v:foreign-zparticles from :entering through: the openings-6i}.

A heat lamp 69 tends to dry the printing cylinder 39 and is suitably located for this purpose. It should be pointed out that in addition to or in substitution for the air jet 67, a plurality of absorbent rollers or brushes could be used for the purpose of cleaning the printing plate 39. A suction line 73 is located in the vicinity of the discharge end of the collimating section 53 to thereby stop 'any unwarranted circulation of air, which would tend to distort the collimated beam of ink particles striking the printing cylinder 39.

A wire corona screen 76, connected to a high pressure voltage source 77, imparts negative ions on to the paper 46. A voltage source 78 of positive potential is connected to the drum 44. Thus, any lint or foreign particles resting on the surface of the paper 46, being negatively charged, are caused to be securely held in position on the paper. Therefore, these foreign particles are prevented from falling off the paper and entering and clogging the openings 60 of the printing cylinder 39. The printing cylinder 39 is preferably grounded, although, it could be connected to a suitable voltage potential source to thereby aid in keeping off foreign particles or dust. The cover 42 is also provided with a suction line 81 which removes the uncleaned air circulating in the vicinity of the printing cylinder 39 and the paper 46.

The printing cylinder or plate 39 is composed of any suitable material which is adapted to etching such as is customary in conventional photographic processes. The plates are fabricated with a thickness in the order of approximately of an inch, but may be either thicker or thinner depending upon the particular application involved. The plates are produced in a manner similar to conventional plates employed in connection with methods of printing such as lithography, letterpress, or gravure. Customary screening methods may be employed to produce the half-tone dots. However, instead of etching only the surface of the printing plate, the plate used in connection with this invention is etched until a hole is produced extending through the plate. Even glass plates could be used, provided they are of a photographic variety such that after exposure to light, the plates could be etched in a manner to produce holes extending through the plates. Plates having as many as 50,000 half-tone holes per square inch may be used.

It is preferable that the surface of the printing cylinder 39, and preferably the inside surface, be serrated. When ink particles are ejected from the collimating section 53 on to the cylinder 39, some particles will not go through the openings 60, but rather will remain or adhere to the inside surface of the cylinder 39. If the inside surface of the cylinder 39 is serrated, the ink particles will tend to adhere more readily to the serrated surface and will be less inclined to drip down over the openings 60, thereby tending to clog the latter.

A modified form of collimating section 165 is shown in Figure 5. The collimating section 165 converges toward its discharge end similar to the embodiment shown in Figure 2. However, the collimating section 165 is provided with a plurality of hollow elongated guide vanes 166 having interior spaces 167 therein. The interior spaces 167, commencing at the interior end of the vanes 166, communicate with enlarged suction chambers 168, which are located adjacent the exterior ends of the vanes 166. The guide vanes 166 converge toward their exterior ends to define a plurality of narrow parallel passageways 169. A plurality of apertures 170 are located in the walls of the vanes 166 adjacent their exterior ends and communicate with the enlarged suction chamber 168. The operation of the modified collimating section 165 is similar to the form shown in Figure 2, in that, the air vehicle transporting the mist of ink particles is removed through the apertures 170, and to some extent, by the wan-s of the hollow vanes 166 which are constructed of porous material. The air so removed is conveyed into the suction chambers 168 which is connected to a suitable vacuum producing source. In the narrow parallel passageways 169 the trajectories of the ink particles become generally parallel, and since the particles have already gained considerable velocity due to the funneling action of the guide vanes 166, they continue their generally parallel direction after leaving the passageways 169. Thus, a plurality of narrow collimated beams of ink particles are produced and strike the printing cylinder 39.

It should be pointed out that a plurality of relatively small parallel beams of ink particles has the characteristic of being better collimated than a single relatively large beam of ink particles. A large beam possesses a great quantity of air vehicle which must necessarily be removed, and the removal of which has a greater distorting effect on the motion of the ink particles. Therefore, more accurate collimation can be effected by a collimating section composed of a plurality of narrow passageways.

Another form of collimating section, designated as 174, is shown in Figure 6. This modification contains a plurality of hollow elongated vanes 175 having interior spaces 176 therein communicating with enlarged suction chambers 177. The vanes 175 have thickened end portions 178 having apertures 179 therein which communicate with the suction chamber 177. The vanes 175 converge, in a manner similar to the vanes shown in the modification of Figure 5, thereby defining a plurality of narrow parallel passageways 180. In this form, a greater focusing action of the flow paths of the ink particles is effected due to the tapering configuration of the vanes adjacent the thickened portion 178.

In Figure 7, a modified form of collimating section 84 is illustrated. This form comprises a plurality of vertical vanes 85 and a plurality of relatively short parallel vanes 86. The vanes 86 are provided with tapered entrance portions 87 and apertures 88 which communicate with suction chambers 89. The tapered entrance portions 87 have a converging action on the ink particles in the same manner as the structures shown in Figure 3 and Figure 6. This converging action aids in the subsequent collimation of the particles. The walls of the vanes 86 define a plurality of narrow parallel passageways 90, spaced preferably less than of an inch apart. The tapered entrance portions 87 may be extended to include the complete length of the vane, but preferably are confined, as shown to only the initial portions of the vanes. In this particular form, the flow paths of the ink particles are collimated not only by the action of the vanes 86, but, also, by means of the vertical vanes 85.

In Figure 8, a modified form of fiuid ejection system and collimating system is shown. In this form, an enclosure 94 is provided, having mounted at one end thereof a plurality of high pressure ejection nozzles 95. The nozzles'95, which eject a marking fluid, such as ink 96, are connected to a trunk line 97 which is connected to a suitable high pressure ink source. The high pressure nozzles 95 eject the ink 96 in a finely atomized form and cause the ink particles to travel toward a plurality of spaced parallel vanes 98 which define a plurality of parallel narrow passageways 99. In this modification, no air or other gas vehicle is used to transport the ink particles. The flow of ink particles is, therefore, collimated, and a plurality of collimated beams of ink particles is directed against a print cylinder 39 and against paper to be printed, in a manner as aforesaid. The walls of the enclosure and the vanes 98 may be provided with suction chambers similar to the construction illustrated in the previously mentioned modifications.

Although, the invention herein disclosed has been discussed in connection with various forms of collimating sections through which ink particles are discharged and which particles come into contact with a rotating printing plate and a rotating print receiving medium, it is obvious that other applications of the novel principles, herein disclosed, can be employed. For example, the print receiving medium and the printing plate could be disposed in superimposed stationary positions, and the collimating section could be oscillated back and forth across the printing plate in linear movements. Also, it shall be stated that although the device herein has been discussed in connection with a printing plate or stencil, the application of the invention is not to be confined in this respect. As is obvious to those skilled in the art, the invention disclosed herein is adapted to numerous applications wherein a stencil is not employed.

Having thus described my invention, I claim:

1. In an apparatus for marking a surface by passing a flow of marking particles through a stencil, a source of flow of marking particles suspended in a gas, a conduit for said flow having its discharge end arranged to be positioned adjacent to the stencil, means associated with the interior of said conduit adjacent the discharge end thereof to aid in collimating the movement of the marking particles in said flow, and means including porous interior surfaces of said conduit, adjacent the discharge end thereof for removing some of the surface flows of said marking particles from the interior surfaces of said conduit to prevent the discharge thereof with the flow of marking particles.

2. In a device of the type described for producing a fine stream of coating particles, a source of a mixture of coating particles suspended in a gas under pressure, a duct for conveying a flow ofsaid mixture, said duct converging toward the discharge end thereof and including means located therein adjacent the discharge end thereof to aid in collimating said fiow of coating particles, and means including a series of holes in the interior walls of said duct adjacent the discharge end thereof of a large enough size for removing from saidflow some of the coating particles smaller than a predetermined minimum size and a part of the gas contained in said flow.

3. In an apparatus for producing a relatively small concentrated stream of coating particles, a source of flow of finely divided coating particles suspended in a gas, a duct for conveying said flow from said source to a discharge area, said duct having at least one pair of opposite walls converging toward the discharge end thereof, the interior walls of said duct adjacent the discharge end thereof being provided with apertures in communication with a sump having a pressure lower than the pressure existing in the gaseous portion of said flow, whereby some of the coating particles smaller than a predetermined minimtun size and a part of the gas contained in said ilow are removed from said flowprior to the discharge of said flow from said duct.

4. In an apparatus for marking a surface by passing a flow of marking particles througha stencil, a source of flow of marking particles suspended in a gas, a conduit for said flow having its discharge end arranged to be positioned adjacent to the stencil, means associated with said conduit to aid in collimating the movement of the marking particles in said flow, said last-mentioned means including a series of apertures arranged in the interior walls of said conduit adjacent the discharge end thereof in communication with a sump having a pressure lower than the pressure existing in the gaseous portion of said flow, whereby a part of the gas contained in said flow is removed from said flow prior to thedischarge of said flow from said conduit. V

5. In an apparatus for producing relatively fine streams of coating particles for depositingon asurface, a source of a mixture of coating particles suspended in a gas under pressure, a duct for conveying a flow of said mixture, said duct converging toward the discharge end thereof, a series of hollow vanes in said duct for collimating and directing the flow of said mixture, said vanes dividing the mixture into a plurality of streams, a series of openings in the sides of said vanes to the interior-thereof, the interiors of said vanesbeing connected to a sump of lower pressure than the pressure of the. gaseous portion of said.

flow whereby a part of the gas in said mixture is removed from saidstrearns prior to the discharge thereof from said duct 6. In an apparatus for producing relatively small highly concentrated streams of coating particles, a source of'a mixture of coating particles suspended in a gas under pressure, a duct for conveying a flow of said mixture from said source to a discharge end thereof, means including converging sides of said duct toward said discharge end to increase the velocity of said flow, means for dividing said flow into a plurality of individual flows, means positioned within said duct adjacent to the discharge end thereof tending to collimate the movement of said coating particles in individual flows, a sump of lower pressure than the pressure of the gaseous portion of saidflow in communication with the interior of said duct adjacent the discharge end thereof and means including said sump for withdrawing from said flow prior to the discharge thereof from said duct a part of the gas contained in said flow.

7. The method of depositing a coating on a surface in accordance with the openings in a stencil which comprises the steps of placing the stencil in front of the surface to be coated, producing a flow of gas containing a suspension of coatingparticles,passing said flow through a duct, removing a part of the gas from said flow prior to the discharge of the flow from said duct, applying collimating forces to the flow of coating particles prior to the discharge of said flow from said duct, and directing the resultant flow of coating particles toward the stencil and surface torbe coated.

8. In an apparatus for marking a surface by passing a flow of marking particles through a stencil, a source of flow of marking particles suspended in a gas, a duct for said flow having its discharge end arranged to be positioned adjacent to the stencil, said duct having at least one pair of opposite sides converging toward the discharge end thereof, a plurality of vanes secured within said duct adjacent the discharge end thereof to aid in collimating the flow of marking particles, and means connected to each of said vanes and in communication with the interior of. said duct adjacent the discharge end thereof for removing a part of the gas in said flow and some of the surface flows of said marking particles from the interior surfaces of said duct to preventthe discharge thereof with the flow of marking particles.

9. The method of claim 7, and furtherincluding the step of removing some of the surface flows of said marking particles from the interior surfaces of said duct to prevent the discharge thereof with the flow of marking particles.

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